Benchmarking magnetized three-wave coupling for laser backscattering

Understanding magnetized laser-plasma interactions is important for magneto-inertial fusion experiments and radiation/particle sources. For ns pulses at non-relativistic intensities, interactions are dominated by three-wave processes, whose coupling coefficients became known only recently when waves propagate at oblique angles. In this work, we benchmark analytical growth rates using particle-in-cell simulations. Excellent agreements are found for a wide range of temperatures, field strengths, and propagation angles when backscattering is mediated by electron-dominant hybrid waves. Systematic comparison is made possible by a rigorous protocol: On the theory side, the initial-boundary value problem of linearized three-wave equations is solved, and transient-time solutions allow effects of growth and damping to be distinguished. On the simulation side, parameters are carefully chosen, and calibration runs are performed to ensure well controlled comparisons. Finally, the analysis is extended to lower-frequency waves, which affect backscattering and cross-beam energy transfer. Model predictions are being tested experimentally at the OMEGA facility.